| The pedicle screw has been used world widely in the treatment of spinal disorders currently for its characteristic of 3-dimensional column fixation, convincing stabilization and maintaining the reconstructed spinal alignment. With the advent of an aging society, the amount of patients suffering from osteoporosis has been rapidly increasing. The population suffering from spinal fractures, infections, degeneration, tumors and so on, with osteoporosis who need to have vertebrae internal fixation will usually encounter such an embarrassing condition that the bone bed was too poor to have pedicle screw fixation done. Thus, how to augment the stability of a pedicle screw fixation seems an urgent and necessary problem to be tackled. In this study, we attempted to use the self-designed enhancer-injector with different number of holes to augment conventional pedicle screws'stability, to compare the differences among different groups, first on mechanical test blocks then further on the cadaveric lumbar specimen,and finally to find a better soluble method to augment the pedicle fixation in osteoporosis condition.. 1 The study of a pedicle screw channel augmentation with acrylic bone cement by enhancer-injectors with different number of holesObjective: To compare the effects of enhancer-injectors with different number of holes on the pedicle screw channel augmention. and to select a better one. Methods: The biomechanical test blocks (The Pacific Research Laboratory Corp. USA) were used in our study as a simulation of the biomechanical character of human osteoporotic cancellous bone. To use the enhancer-injector with different number of holes to augement a pedicle screw channel in different ways. The experimental groups can be divided into the following five groups as a 4-sided-hole, 6-sided-hole, 8-sided-hole, local augmentation groups, and a full-length augmentation group respectively. The control group referred to is that where pedicle screws were inserted without any cement augmentation. A 3.5 mm diameter hand drill was used to prepare the pedicle screw channel in the biomechanical test blocks to the upper surface with a depth of 45 mm. In the experimental groups, the novel sided-holes or straight-hole were inserted into the block along the prepared channel. In the sided-hole groups, the sheath was inserted along the prepared channel, and 2.5ml of ABC was injected into the sheath. Then a steel-rod was put into the cannulated sheath to push out the remainder of the cement to the testing block. In the full-length group, the straight-hole sheath was inserted into the channel along the prepared hole and to inject the cement as withdrawing. Before the cement was hardened, the CD HORIZON M8 pedicle screw (size: length 45mm, diameter 6.5mm; Sofamor Danek Corp.) was inserted into the channel with a manual torque wrench at a rate of 3 rev/min evenly. The pedicle in the control group was inserted into the block without any cement injection. The maximum insertion torque was recorded. The pedicle screw's maximum axial pullout strength in each group was tested by a MTS 858 machine after 24 hours. Results: The pedicle screw's maximum pullout strength of each group augmented by a 4-sided-hole, 6-sided-hole, 8-sided-hole, and a full-length novel device, which was respectively higher than that of the control group. Among the experimental groups, the 8-sided-hole group had lower screw pullout strength than the other threes, and the difference was statistically significant. There were no differences between the 4-sided-hole, 6-sided-hole and the full-length groups each. There also was no difference between the insertion torque. The distribution of the ABC injected by enhancer-injector with different number of holes presented regularity. The cement of the 4-sided-hole group distributed along the distal one third length of the screw. And in the 6-sided-hole group, the ABC distributed from the proximal one-third point of the screw to the distance, and in the 8-sided-hole group, the ABC distributed along the proximal one third length. Conclusion: The enhancer-injectors with different number of holes can be used to augment the pedicle screw channel by combining with ABC. The pedicle screw augmented by a 4-or 6-sided-hole sheath may have similar maximum axial pullout strength as the full-length cement injection with the same amount of 2.5ml cement. However, the 8-sided-hole enhancer-injector may result in relatively lower pullout strength and has the possibility of cement extravasation as well as cement solidarization near the screw head. Both the 4 and 6-sided-hole novel devices could be used to augment the pedicle screw channel.2 The study of a pedicle screw channel augmentation with calcium phasphite cement by enhancer-injectors with different number of holesObjective: To evaluate the effects of enhancer-injectors with different number of holes on the pedicle screw channel augmentation. Methods: The biomechanical test blocks (The Pacific Research Laboratory Corp. USA) were used in our study as a simulation of the biomechanical character of human osteoporotic cancellous bone. To use the enhancer-injector with different number of holes to augement a pedicle screw channel in different ways. The experimental groups can be divided into the following five groups as a 4-sided-hole, 6-sided-hole, 8-sided-hole, local augmentation groups, and a full-length augmentation group respectively. The control group referred to is that where pedicle screws were inserted without any cement augmentation. The 3.5 mm diameter hand drill was used to prepare the pedicle screw channel in the biomechanical test blocksrly to the upper surface with a depth of 45 mm. In the experimental groups, the novel sided-holes or straight-hole were inserted into the block along the prepared channel. In the sided-hole groups, the sheath was inserted along the prepared channel, and 2.5ml of CPC was injected into the sheath. Then a steel-rod was put into the cannulated sheath to push out the remainder of the cement to the testing block. In the full-length group, the straight-hole sheath was inserted into the channel along the prepared channel and to inject the cement as removing. Before the cement was hardened, the CD HORIZON M8 pedicle screw (size: length 45mm, diameter 6.5mm; Sofamor Danek Corp.) was inserted into the channel with a manual torque wrench at a rate of 3 rev/min evenly. The pedicle in the control group was inserted into the block without any cement injection. The maximum insertion torque was recorded. The pedicle screws'maximum axial pullout strength in each group was tested by a MTS 858 machine after 24 hours. Results: The distribution of the CPC injected by enhancer-injector with different number of holes present regularity. The cement of the 4-sided-hole group distributed along the distal one third length of the screw. And in the 6-sided-hole group, the CPC distributed from the one third point of the screw to the distance. In the 8-sided-hole group, the CPC distributed along proximal one third length. The pedicle screw's mean maximum pullout strength of each group augmented by a 4-sided-hole, 6-sided-hole, 8-sided-hole, and a full-length novel device, which was respectively higher than that of the control group. Among the experimental groups, the 8-sided-hole group had lower screw pullout strength than the other threes, and the difference was statistically significant. There were no differences between the 4-sided-hole, 6-sided-hole and the full-length groups each. There also was no difference between the insertion torque. Conclusion: The enhancer-injector with device can be used to augment the pedicle screw channel by combining with CPC, a pedicle screw, and augmented by a 4-or 6-sided-hole. They all have similar maximum axial pullout strength as the full-length cement injection with the same amount of cement which was 2.5 ml. However, the 8-sided-hole novel device may result in a lower pullout strength and has the possibility of cement extravasation as well as cement solidarization near the screw head. Both the 4 and 6-sided-hole novel devices could be used to augment the pedicle screw channel.3 The evaluation of axial pullout strength of the pedicle screw augmented with ABC and CPC by sided-holes enhancer-injector of the same type.Objective: To compare the effects of a pedicle screw fixation augmented locally with ABC and CPC cement via enhancer-injector of the same sided-holes number .Methods: The osteoporotic biomechanical test blocks made in the USA by the Pacific Research Corp. were used here as a simulation for the biomechanical characteristics of an osteoporotic cancellous vertebral bone. Pedicle screws were augmented by a novel 4-sided-hole, 6-sided-hole, 8-sided-hole device with ABC and CPC respectively. A 3.5 mm diameter hand drill was used to drill into the biomechanical test blocks and all of the blocks in our test were drilled to a depth of 45 mm. The sided-hole novel devices were inserted into the block perpendicularly to the block upper-surface along the prepared channels, and then were connected to a 5 ml capacity syringe. Having mixed ABC cement to a tooth-paste state, 2.5ml of cement was injected into the novel device, then the syringe was removed and the use of a custom-designed rod to push the remainder of the cement. CPC cement was injected into the biomechanical test blocks with the same procedures of the ABC cement. Results: The pedicle screws'maximum pullout strength of the groups augmented with ABC cement had a respective statistical difference than with groups augmented by CPC cement with a 4-sided-hole, 6-sided-hole, 8-sided-hole novel device. SPSS 11.5 statistical software package was used to analyze the data. Conclusion: Both ABC and CPC can be used to augment the pedicle screw via enhancer-injector and by the same type of the novel sided-hole device, a pedicle screw locally augmented with ABC had higher mean maximum axial pullout strength than CPC.4 The biomechanical study of a pedicle screw fixation augmented by ABC and CPC respectively on fresh-frozen cadaveric osteoporotic vertebrae by enhancer-injectorObjective: To study the effects of the enhancer-injectors with different number of holes on pedicle screw fixation augmentation by ABC and CPC on the cadaveric osteoporotic vertebrae. Methods: Forty-two lumbar vertebrae from 9 human fresh-frozen, donated corpses were collected. Discs and soft tissues were removed completely and the 3 vertebrae with severe deformation were excluded. The BMD was also examined by DEXA. The total of 42 vertebrae was randomized into two groups. One group was ready to test the axial pullout strength, and the other group was ready to do the cephaladcaudal cyclic fatigue test. For each group, they were randomized into seven subgroups even further. Among the groups, the BMD value showed no stastically different each. (P>0.05)The experimental groups were augmented with ABC by 4-sided-holes, 6-sided-holes, full-channel-length, and with CPC by 4-sided-holes, 6-sided-holes, full-channel-length. The control group was referred to by that group where the pedicle screws were inserted without any cement. According to the"Chevron pointing"method, the pedicle screw channel of a 45 mm length was conventionally prepared by a 3.5 mm diameter hand drill. The sided-hole sheath was inserted into the pedicle screw channel, and a total of 2.5 ml ABC or CPC was injected into each pedicle via the novel side-hole device. The full-length pedicle screw channel augmentation was carried out by the straight-hole sheath by injection as withdrawing. The X-ray and CT renconstruction were carried out. After 24 hours conservation at room temperature, the maximum axial pullout strength and cephalocaudal cyclic fatigue test were carried out by MTS 858 machine. Results: By X-ray and CT renconstruction, it can be seen that the cement of the 4-sided-hole group mainly distributed in the vertevrae body, and in the 6-sided-hole group, the cement distributed both in the latter of the vertebral body and the pedicle, in the full-channel group, it distributed along the whole channel. In the axial pullout test, the 6-sided-hole group had a significant higher pullout strength than that of the 4-sided-hole group and it showed no statistical difference between 6-sided-hole group and full-length group. In the CPC augmentation group, we got the similar results from the CPC augmentation group. In the cephalocaudal cyclic fatigue test, the pedicle screws augmented by 6-sided-hole novel device had the highest mean maximum axial pullout strength among the ABC augmentation groups, and it was similar in the CPC cement augmentation groups. In the cephalocaudal cyclic fatigue test, the 6-sided-hole group had the least displacement of pedicle screw head, and had showed a significant difference from the other groups. Conclusion: The 6-sided-hole enhancer-injector could provide as stable as the full-length-channel group, and has the higher axial pullout strength. It has also remained the screw-bone interface, and can be recommeded as an effective way to augment the screw channel, especially in the osteoporotic conditions, either with ABC or CPC.
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